1. Field of the Invention
This invention relates to combining a single photon emission computed tomographic SPECT scanner with a computed tomographic CT scanner, and more particularly, providing a Combined Single Photon Emission Computed Tomographic CSPECT Scanner which convolves the data obtained from the SPECT scanner with the anatomical data obtained from the CT scanner.
2. Description of the Prior Art
This invention is directed to nuclear medicine imaging equipment. Presently most nuclear medicine studies consist entirely of a plainer imaging procedure. After being injected (usually intravenously) with a radio labeled pharmaceutical the patient is positioned under, in front-of, or on-top-of a nuclear medicine gamma camera (Anger camera). Images are formed in a direct relationship to radionuclide concentration within the body. Very little, if any depth information is retained in the final images. Occasionally, more sophisticated images may be obtained by rotating the camera about the patient, and collecting and analyzing the tracer distribution information by computer. The result is called single photon emission computed tomography (SPECT). Today with the advent of mononuclonal antibody tracers appearing onto the commercial market, an increased number of SPECT imaging procedures are being ordered. The tracer distribution in a given patient may vary widely from anatomical area to anatomical area, and change also with time. Normal physiologic tracer accumulation in large organs like the liver or the bone marrow are used as landmarks to determine where pathophysiologic tracer accumulation accumulates.
For example, a patient with known colon cancer may get injected with a tracer dose of a radiolabeled monoclonal antibody sensitive to both ovarian and colon cancer. SPECT images of the patient are typically obtained immediately and then again 96 hours after injection. Transverse, coronal and sagital SPECT images are usually processed and reviewed by the attending nuclear medicine physician shortly thereafter, in an attempt to determine sights of metastatic disease. Vague anatomic landmarks are provided by normal physiologic tracer accumulation, and are deemed normal. The physical location of the abnormal tracer accumulation is reported relative to normal known organ boundaries. The anatomical information provided by SPECT is poor. The resolution is 1.5-2.0 cm and many normal organ boundaries are not even identified. If the nuclear medicine physician is capable of interpreting computed tomography (CT) images and if the patient had recent CT imaging, the physician might attempt to cross correlate the findings on both studies. Unfortunately, the patient may not have been in the same position for the CT scan as the SPECT scan, or the gantry of the CT scanner may have been at a different angle than was used to do the SPECT study. Ultimately, it is variation in patient position which makes direct mathematical superposition of these studies impossible. Limited crude superposition is now becoming possible using the latest computer techniques. Currently, one can take two similar images, one from CT and one from SPECT, and superimpose them, using sophisticated software on a workstation like the SUN, or a powerful desktop computer. Ultimately, no matter what system is used, final image alignment is done "by eye". Again, one should note that, variation in patient position makes exact superposition unlikely.
Most institutions do not even bother to take the time to superimpose SPECT and CT information. The current state of the art is to view the SPECT image information, and if it is present, also view available CT (or Magnetic Resonance MR) data. One then superimposes these two data sets mentally (in one's head). Obviously this method is less than optimum, and results in significant errors.
Accordingly, it is an object of the present invention to have an imaging device which would obtain the SPECT images and the CT images more or less simuataneously, in a single examination, with the patient in a fixed position.
It is another object to have the SPECT images convolved directly with the anatomical images produced by its own CT scanner.
Other novel features which are characteristic of the present invention will be better understood from the following description considered in connection with the accompanying drawing in which preferred embodiments of the invention are illustrated. It is expressly understood however, that the drawing is for the purpose of illustration and description only and is not intended as a definition of the limits of the invention.